German patent publication 197 54 286 discloses a method and an arrangement for controlling a drive unit of a vehicle. Here, the degree of actuation of an operator-controlled element, which is actuable by the driver, is detected and a desired value for the torque of the drive unit is formed from this degree of actuation.
Furthermore, road speed controls are known which require a specific torque from the internal combustion engine for maintaining a desired speed of a vehicle. During the active operation of the road speed controller, if the driver wants to go faster than the set speed, for example, in order to initiate a passing operation, then the driver demands a higher torque from the engine by actuating the accelerator pedal. For this purpose, the driver must actuate the accelerator pedal so far that the required torque of the engine, which results therefrom, is greater than the torque required by the road speed controller. Up to this operating point of the accelerator pedal, there is therefore a lost motion or dead travel in the accelerator pedal with which the reaction of the vehicle is not changed.
The method of the invention and the arrangement of the invention for controlling a drive unit of a vehicle afford the advantage with respect to the foregoing: that the desired value for the torque is compared to an input value for the torque which is just then required by the road speed controller; that, with the control of the drive unit, the torque of the drive unit only then approaches the desired value when the desired value exceeds the input value; and that the trace of the desired value for the torque as a function of the degree of actuation of the operator-controlled element is so selected that a pregiven value for the degree of actuation of the operator-controlled element is not exceeded at an intersect point of the trace of the desired value for the torque and the input value required just then by the road speed controller. In this way, the lost motion or dead travel can be reduced with the actuation of the operator-controlled element up to exceeding the input value required by the road speed controller. The vehicle can then react more quickly to a driver command after increasing the torque beyond the input value required by the road speed controller, for example, to initiate a passing maneuver.
It is especially advantageous when the trace of the desired value for the torque drops below the input value by, at the most, a pregiven difference value. In this way, the pregiven value for the degree of actuation of the operator-controlled element can be realized with the least possible computation complexity via a simple displacement of a part of the characteristic line for the trace of the desired value.